Compressor unloader



B. S. AIKMAN COMPRESSOR UNLOADER Filed Sept. 4, 1935 April 12, 1938.

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wm b9 Q INVENTOR EURTDN s. AIKMAN NEY I ATTOR Patented Apr. 12,1938

UNITED STATES COMPRESSOR UNLOADER -Burton s. Aikman, Wilkinsburg, Paassignor to The Westinghouse Air Brake Company, Wilmerding, Pa., acorporation of Pennsylvania Application September 4, 1935, Serial No.39,133

, 8 Claims.

This invention relates to a control system for a fluid compressor drivenby an internal combustion engine.

It is the principal object of this invention to 5 provide a controlsystem for a fluid compressor driven by an internal combustion engine,the control system comprising unloading means associated with thecompressor and operated by the vacuum in the inlet passage of theengine.

10 A further object of this invention is to provide a compressor controlsystem of the type referred to and which incorporatesmeans responsive tothe pressure of the fluid compressed by the compressor and controlling acommunication between 5 the engine intake passage and the unloadingmeans, whereby the unloading means is controlled by the engine intakepressure in response to variations in the pressure of the fluidcompressed by the compressor.

Another object of this invention is to provide a compressor controlsystem of the type referred to and which incorporates means subject tothe pressure of the fluid compressed by the compressor and subject alsoto the vacuum in the 25 inlet passage of the engine and controllingapassage between the engine inlet passage and the unloading means.

A further object of this invention is to provide a compressor controlsystem of the type referred 30 to and having means subject to thepressure of the fluid compressed by the compressor, said means beingbiased to a position to maintain the compressor loaded and being movableon a predetermined increase in the pressure of the fluid com- 35 pressedby the compressor to a position to effect unloading of the compressor,said means being subject also to the vacuum in the engine inlet passageon movement to the unloading position,

whereby said means is maintained invsaid unload- 40 ing position untilthe pressure of the fluid compressed by the compressor is reduced to avalue substantially less than that required to eflect movement of thesaid means from the loading position to the unloading position.

45 other objects of the invention and features of novelty will beapparent from the following description taken in connection with theaccompanying drawing, the-single flgure of which is a diagrammatic-view,partly in section, of a fluid 50 compressor equipped with one embodimentof the control system provided by my invention.

Referring to the drawings compressor is indicated generally by thereference character. I and is driven by an internal combustion engine3,,

65 which may be of any suitable well-known conloading'device 36 isprovided and controls the struction and is provided with a fuel inletpassage or manifold 5 through which fuel is supplied to the cylinders ofthe engine.

The compressor I comprises a body having a crank case chamber I formedtherein, and having a cylinder ll associated therewith and provided witha bore in which is reciprocably mounted a piston It. The upper end ofthe bore in the cylinder ll is closed by means of a cylinder head l5,which has a chamber it formed therein, and in which is positioned anexhaust valve l8 which is urged by means of a spring 22 into engagementwith a seat I 9'surrounding a passage communicating with the chamberabove the piston l4 and with the chamber i6 in the cylinder head 15 I 5.The chamber I6 is connected with a reservoir by way of a pipe 26.

The wall of the cylinder I I has an annular passage formed thereinsurrounding the bore in the cylinder and communicating with this bore byway of a plurality of ports 32 which extend through the wall of thecylinder and which communicate with the bore at a point just above thetop of the piston I 4, when the piston is at the lower end of its rangeof movement. A pas-' sage 35 is provided in the wall of the cylinder ll25 and communicates with the crank case chamber l0 and with the'passage30.

A combined air strainer and compressor un- 28w of fluid from theatmosphere to the passage The combined air strainer and unloading'device36 comprises a body section indicated generally by the referencecharacter 39, and having a sub- 35 stantially cylindrical peripheralportion 39 and a central portion 40 which is connected with theperipheral portion 39 by means of a radially extending portion 4|.

The central portion 40 has a valve chamber 43 40 formed therein in whichis mounted a valve 45 having a fluted stem positioned in a boreextending through the central portion 40, and having a head adapted toseat on a seat surrounding the bore in which the fluted stem ispositioned.

A pair of annular perforated members 41 and 48 are positioned in thecavity between the central portion-40 and the peripheral portion 39 ofthe body section 98 and have placed between them a quantity of asuitable air straining mate- 50 rial. such as curled hair, indicated at49. The member 481s held in position by means of the cover plate 5|,which has a projecting portion 53 formed thereon and extendingwithin-the peripheral portion 39 andengaging the member 48. 55

-an annular flange 56 engaging the inner margin of the cover plate 5|.The exposed end of the casing section 55'is threaded and is adapted tobe screwed into a threaded opening in the wall of the cylinder II. sothat a passage 58 through the casing section 55 communicates with thepassage '39 in the wall of the cylinder I I. I

The combined air strainer and compressor unloading device 36 includes amovable abutment in the form of a diaphragm 69, clamped between thecasing section 39 and a casing section. 62, and having on one sidethereof a chamber 64 in which is mounted a follower 95 which engages oneside of the diaphragm 69 and to which is secured the end of the stem ofthe valve 45. A spring 91 is also mounted in the chamber 64 and engagesthe follower 55 so as to normally urge the follower to move to the leftand thus move the valve 45 away from its seat. I

The diaphragm 69 has onthe opposite side thereof a chamber, 69 which isconstantly con-' nected with a chamber I9 on one side of the airstraining means 49 by way of passages I2, and

which communicates with the valve chamber 43 by way of the bore in whichthe valve 45 is mounted. The chamber 14 on the opposite side of the airstraining means 49- is in communication with the atmosphere by way of apassage 16.

The control system provided by this invention includes a control device,indicated generally by the reference character 89, and which as showncomprises amovable abutment in the form of a diaphragm 8| clampedbetween a casing section 92 and a body section 94, and having on oneside thereof a chamber 86 which is constantly con nected to the mainreservoir 25 by way of a pipe 81. The diaphragm 8| has on the other sidethereof a chamber 99 in which is positioned a plunger 92.

The body section 94 has a wall 9| extending across the chamber 99 andhaving a passage 94 formed therein which is constantlyconnected with theengine -inlet passage 5 by way of a pipe 95. The end of the passage 94is surrounded by a seat 96 and a ballvalve 98 is held in engagement withthe seat 96 by means of a spring 99 acting through a valve cage I99. Thevalve cage I99 is moved against the spring. 99 by means of the plunger92 acting through the push pins I92, which extend through openings inthe wall 9I which extends across the chamber 99.

The chamber 99 is constantly connected with the chamber 64 of thecombined air strainer and compressor unloading device 36 by way of apipe I95, and is constantly connected with the atmosphere by way of apassage I96, which has a flow capacity substantially less than that ofthe passage 94 and pipe 95 by means of which the chamber 99 is connectedto the engine inlet passage 5.

In the operation of the system, assuming that the compressor is idle andthat the reservoir 25 is at atmospheric pressure, the spring 99 of thecontrol device 99 will maintain the ball valve 98 in engagement with theseat 96, while the chamber 99 will be at atmospheric pressure as it is.in communication with the atmosphere byway of the passage I96. v

Thechamber 64 of the combined air strainer and unloading device 36 willalso beat at-mos pheric pressure as it is in communication with thechamber 99 of the control device 89 by way of the pipe I 95, and thespring 61 will maintain the valve 45 in the position in which it isshown in the drawing, in which position communication is permittedbetweenthe valve chamber ,43 and the atmosphere through the airstraining means 49. This permits fluid to be supplied to the passage 39from the atmosphere, and effects loading of the compressor.

When the engine 3 is started the crank shaft of the compressor isrotated, and the piston 14 is caused to reciprocate in the bore in thecylinder I I. On upward movement of the piston I4 from the position inwhich it is shown in the drawing, the piston cuts oil communicationthrough the ports 32, and on further movement of the piston the fluid inthe chamber above the piston is compressed and the pressure of the fluidacting upon the exhaust valve I8 causes this valve to be moved upwardlyaway from the seat I9 against the spring 22 so that air flows from thepiston chamber to the exhaust valve chamber I9, and therefrom by way ofthe pipe 26 to the reservoir 25.

On downward movement of the piston I4 the exhaust valve I9 is moved intoengagement with its seat I9 by the spring 22 so as to cut off the flowof fluid from the exhaust valve chamber I9 to the chamber in the bore inthe cylinder II above the piston I4, with the result that a partialvacuum is created in the chamber above the piston. When the piston I4moves to its lower position, in which position the ports 32 are againuncovered, fluid flows from the passage 39 through the ports 32 to thechamber above the piston. This produces a reduction in the pressure ofthe air or fluid in the passage 39 and causes air or fluid to flow tothis passage from the valve chamber'43, and on a reduction in thepressure of the fluid inthe valve chamber-43, fluid will be suppliedthereto from the atmosphere by way of the passage I6, the chamber 14,through the air straining means 49 to the chamber I9, and therefrom byway of the passages 12 to the chamber 69, and thence past the flutedstem of the valve 45 to the valve chamber 43.

On the next upward stroke of the piston I4 the air or fluid which is inthe chamber above the piston I4 will be compressed, and this processwill be repeated with each revolution of the crank shaft of thecompressor.

During operation of the engine 3 a partial vacuum will be established inthe engine inlet passage or manifold 5,'and this vacuum will becommunicated to the pipe 95 and the passage 94, but it will not becommunicated to the chamber 99 in the control device 89 at this time asthe ball valve 98 is held in engagement with the seat 96 so as to cutoif communication between the passage 94 and the chamber 99.

After a period of operation of the compressor the pressure of the fluidin the reservoir 25 will have increased to a predetermined value suchthat the pressure of the fluid in the chamber 86 exerts a force on thediaphragm 8| which exceeds that exerted by the spring 99, acting on theother side of the diaphragm 9| through the valve cage I99, the pushpinsI92, and the plunger 92. The diaphragm 8I will thereupon be forceddownwardly againstthe spring 99, and the ball valve element 99 will bemoved by gravity away from theseat 96. i

As soon as the'ball valve 99 moves away from will be drawn through thepassage 94 and-the pipe 95 to the inlet passage 5, and a partial vacuumwill be established in the chamber 99, as the rate at which fluid iswithdrawn from the chamber 99 through the passage 94 and the pipe 95substantially exceeds that at which fluid is supplied to the chamber 99from the atmosphere by way of the passage I96.

The resulting reduction in the pressure of the fluid in the chamber 99increases the force effective to urge the plunger 92 downwardly and theplunger will thereafter be moved very rapidly until it engages the wall9|, which limits downward movement of the plunger 92.' i

It will be seen, therefore, that as soon as the valve 99 is moved awayfrom the seat 96 as a result of an increase in the pressure of the fluidin the reservoir 25, it will be moved to the full open position veryrapidly due to the reduction in the pressure of the fluid in the chamber99 which occurs when the valve 99 is moved away from its seat. I

On a reduction in the pressure of the fluid in the chamber 99, a similarreduction in the pressure of the fluid in the chamber 69 will beeffected, as the chamber 64 is in communication with the chamber 99 byway of the pipe Hi5,

and, on a reduction in the pressure of the fluid in the chamber 69, thediaphragm 69 will be moved to the right against the spring 611 by thepressure of the atmosphere in the chamber 69 on the opposite side of thediaphragm, and the valve 96 will be moved into engagement with the seatsurrounding the passage in which the valve is mounted, thus cutting oifthe flow of fluid from the atmosphere to the valve chamber 99. This cutsoff the supply of fluid to the compressor and causes the compressor tobe unloaded, with the result that on continued operation of thecompressor no fluid will be compressed by it as long as the valve 45 isin the seated position.

The compressor will continue to run in the unloaded condition until thepressure of the fluid in the reservoir 25 is reduced to a value suchthat the force exerted by the diaphragm M as a result of thefluid underpressure in the chamber 96 acting upon it, and as a result of thepartial vacuum in the chamber 99 acting upon it, is less than the forceexerted by the spring 99 acting through the plunger 92 and tending tomove the diaphragm upwardly.

When thepressure of the fluid in the reservoir.

95 has been reduced to this value the ball valve 99 will be moved intoengagement with the seat 96 so as to cut ofi communication between thepassage 99 and the chamber 99. This cuts oil communication between thepassage 99 and the chamber 99, and permits the chamber 99 to be restoredto atmospheric pressure by the flow of fluid from the atmosphere throughthe passage l96. When the chamber 99 is restored to atmospheric pressurethe force exerted by the diaphragm 9i acting through the plunger 92 andtending to move the valve cage I99 downwardly against the spring 99 willbe decreased, with the result that the spring 99 will hold the ballvalve 99 firmly in engagement with the seat 96.

When the chamber 99 is restored to atmospheric pressure a similarincrease will be efiected in the pressure of the fluid in the chamber 64of the combined air strainer and unloading device 36, and the diaphragm69 will thereupon be moved to the left by the spring 61 so that thevalve 45 will be moved away from its seat to again permit the flow offluid from the atmosphere to the" valve chamber 93, thus eifectingloading of the compressor.

The cylinder wall of the compressoris provided with a passage 35, whichextends between the passage 39 and the crank case chamber l9, so that ona reduction in the pressure of the fluid in the passage 39 as result ofoperation of the compressor, fluid will flow from the crank case chamberill to the passage 39. This produces a partial vacuum in the crank casechamber l9 and causes air to tend to flow into the crank case, chamberfrom the atmosphere through the joints in the walls of the crank case,

thereby opposing the escape of lubricant from the crank case through thejoints in the walls of the crank case chamber.

From the foregoing it will be seen that the compressor control systemprovided by this invention incorporates means responsive to the pressureof the fluid compressed by the compressor and to the pressure of thefluid in the inlet passage of the engine which drives the compressor;this means controlling the loading and unloading of the compressor.

It will be seen also that the unloading control means is responsive onlyto the pressure of the fluid compressed by the compressor when thispressure is below a predetermined value, and that upon an increase inthis pressure to a value above said predetermined value the controlmeans is rendered subject to the pressure of the fluid in the engineinlet passage and is operated to effect unloading of the compressor,whereby the control means is maintained in the position to effectunloading of the compressor until the pressure of the fluid compressedby the compressor falls to a value substantially lower than thatoriginally required to effect movement of the control means to aposition to effect unloading of the compressor. 7

This insures that there will be a pressure differential between thepressure at which the compressor is unloaded and the pressure at whichthe compressor is loaded. This construction also insures that when thevalve means of the unloading control means is moved from the closedposition to the open position, it will be moved very rapidly after theinitial movement thereof away from the closed position, and that onmovement of this valve means to the closed position from the openposition it will be held firmly in engagement with its seat.

It will be seen also that the control device provided by this inventionopens a passage through which air is supplied to the engine inletpassage when the control device moves to the position in which thecompressor is unloaded. The system operates, therefore, to vary themixture of the fluid supplied to the engine in response to the loadingand unloading of the compressor, the supply of air being increased whenthe compressor is unloaded, at which time the load on the engine is at aminimum. As soon as the compressor is loaded, however, the supply of airto the engine inlet passage through this passage is cut off, and thishas theefiect of enriching the mixture of the fuel supplied to theengine when the engine is subjected to load.

While one embodiment of the control system provided by this inventionhas been illustrated and described in detail, it should be understoodthat the invention is not limited to these details of construction, andthat numerous changes and modifications may be made without departingfrom the scope of 'the following claims.

claim as new and desire to secure by Letters Patent, is:

1. In a control system for a fluid compressor driven by an internalcombustion engine the combination of a fuel inlet passage for theengine, unloading means associated with the compressor, a control devicefor controlling operation of the unloading means, said control devicecomprising means subject to the pressure of the fluid compressed by thecompressor and biased to a position to efiect loading of the compressorand being moved to a position to effect unloading of the compressor on apredetermined increase in the pressure of the fluid compressed by thecompressor, said means being subject to the pressure of the fluid in theengine inlet passage after movement away from the loading position,whereby the pressure required to move said means from the loadingposition exceeds the pressure required to maintain said means away fromthe loading position, and whereby the compressor remains unloaded untilthe pressure of the fluid compressed by the compressor is reduced to avalue less than that required to effect unloading of the compressor. V

2. In a control system for a fluid compressor driven by an internalcombustion engine, in combination, a fuel inlet passage for the engine,unloading means for the compressor, movable abutment means subject tothe opposing pressures of the atmosphere and of the fluid in a chamberfor controlling operation of the unloading means, means for supplyingfluid to said chamber, and movable abutment means subject to theopposing pressures of the fluid in said chamber and of the fluidcompressed by the compressor and controlling communicationbetween saidchamber and the engine inlet passage.

3. In a control systemior a fluid compressor driven by an internalcombustion engine, in combination, a fuel inlet passage for the engine,unloading means for the compressor, movable abutment'means subject tothe opposing pressures of the atmosphere and of the fluid in a chamberfor controlling operation of the unloading means, means for supplyingfluid from the atmosphere to said chamber at a given rate, and movableabutment means subject to the opposing pressures of the fluid in saidchamber and of the fluid compressed by the compressor and controlling acommunication between said chamber and the engine inlet passage throughwhich fluid may flow from I the chamber to the engine inlet passage at arate more rapid than said given rate.

4. In a control system for a fluid compressor driven by an internalcombustion engine, in combination, a fuel inlet passage for the engine,unloading means for the compressor, biasing means associated with theunloading means and yieldingly urging said unloading means to a positionto effect loading of the compressor, movable abutment means subject tothe opposing pressures of the atmosphere and of the fluid in a chamberand operated on a reduction in the pressure of the fluid in said chamberto effect movement of the unloading means to a position to unload thecom pressor, means for supplying fluid to said chamber, and movableabutment means subject to the opposing pressures of the fluid in saidchamber and of the fluid compressed by the compressor sures of theatmosphere and of the fluid ina chamber and operate on a reduction inthe pressure of the fluid in said chamber to effect movement of theunloading means to a position to unload the compressor, means forsupplying fluid from the atmosphere to said chamber at a given rate, andmovable abutment means subject to the opposing pressures of the fluid insaid chamber and of the fluid compressed by the compressor andcontrolling a communication between said chamber and the engine inletpassage through which fluid may flow from said chamber to the engineinlet passage at a rate more rapid than said given rate.

6. In a control system for a fluid compressor driven by an internalcombustion engine, in combination, a fuel inlet passage for the engine,unloading means for the compressor, yielding means urging said unloadingmeans to a position to effect loading of the compressor, movableabutment means subject'to and operated on a reduction in the pressure ofthe fluid in a chamber to move the unloading means to a position toeffect unloading of the compressor, means for supplying fluid to saidchamberyand means responsive to the opposing pressures of the fluidcompressed by the compressor and of the fluid in said chamber forestablishing communication between said chamber and the fuelinlet-passage.

7. In a control system for a fluid compressor driven by an internalcombustion engine, in combination, a fuel inlet passage for the engine,unloading means for the compressor, a movable abutment subject to thepressure of the fluid in a chamber for operating the unloading means,means for supplying fluid to said chamber, valve means for controllingcommunication between said chamber and the fuel inlet passage, meansresponsive to the pressure of the fluid compressed by the compressor formoving said valve means to a position to establish communication betweensaid chamber and said inlet passage, and means subject to pressure ofthe fluid in said chamber and opposing movement of the valve means bythe means responsive to the pressure of the fluid compressed by thecompressor.

8. In a control system for a fluid compressor driven by an internalcombustion engine having a fuel inlet passage associated therewith, amovable abutment subject to and operated on a reduction in the pressureof the fluid in a chamber to unload the compressor, means for supplyingfluid to said chamber, and a movable abutment subject to the opposingpressures of the fluid compressed by the BURTON S. m

